In a vehicle, the powertrain or powertrain system refers to the components that provide the power to propel the vehicle. These components include the engine, transmission, drive/propeller shaft, differentials, and final drive. In operation and for an internal combustion engine, the engine combusts a fuel to generate mechanical power in the form of a rotating a crankshaft. The transmission receives the rotating crankshaft and manipulates the engine speed (i.e., the rotation of the crankshaft) to control a rotation speed of the drive/propeller shaft, which is also coupled to the transmission. The rotating drive shaft is received by a differential, which transmits the rotational power to a final drive (e.g., wheels) to effect a movement of the vehicle. In an automobile, the differential enables the wheels, on a shared axle, to rotate at different speeds (e.g., during a turn, the outer wheel spins faster relative to the inner wheel to allow the vehicle to maintain its speed and line of travel).
Because the engine speed does not always equate to a desired final drive speed (and, consequently, vehicle speed), the transmission manipulates the engine speed to affect the drive shaft speed for a desired vehicle speed. To achieve a different drive shaft speed relative to the engine speed, some transmission systems utilize a plurality of gears that either increase or decrease the drive shaft rotational speed relative to the engine speed (e.g., 2:1, which indicates that the engine is rotating twice as fast as the output speed). Gear selection can be done by an operator of the vehicle or automatically without operator input and can be based on engine speed, vehicle speed, throttle position, and load on the engine. For example, during highway driving, the transmission may use a high gear that provides a relatively higher transmission output speed (i.e., speed of propeller/driver shaft) than a low gear to maintain/achieve the relatively greater vehicle speed needed for highway driving. As such, the transmission allows the vehicle to achieve desired vehicle speeds and powers largely independent of the engine speed. However, transmission operation and control strategies therefor are independent from engine operation and control strategies for the engine, such that inefficiencies exist from operation of the engine-transmission system.